Current treatment for genotype 1 HCV infection with pegylated interferon (PEG IFN) and ribavirin (RBV) is effective in less than 50% of patients. The advent of direct-acting antiviral agents that target replication of HCV promises to improve therapy for the disease. Telaprevir is a new peptidomimetic serine protease inhibitor that specifically targets the NS3/4a HCV serine protease to cause rapid reduction in HCV RNA levels. Three Phase II Protease Inhibition for Viral Evaluation (PROVE) studies have assessed the efficacy and safety of telaprevir in genotype 1 patients. The studies examined sustained virological response (SVR) rates and also the adverse events related to the use of this drug in different groups. The results of these studies suggested that the addition of this specific protease inhibitor to PEG IFN alfa-2a and RBV can significantly improve the results of treatment in patients affected with chronic HCV infection with genotype 1, when compared with the standard treatment, PEG IFN alfa-2a and RBV alone. The key observations in these Phase II trials of telaprevir were higher rate of SVR above current standard of care (61-69% for T12PR24 treatment-naive patients compared with 46-48% for standard of care in naive patients). Low rates of relapse were observed in T12PR24-treated patients (2-14% vs 22-23%). The studies suggest that the duration of treatment could be reduced for rapidly responsive naive patients from 48 to 24 weeks while maintaining improved SVR rates. RBV remains an essential component of treatment with protease inhibitors combined with PEG IFN. The main adverse reactions of note with its use were rashes, anemia and nausea.